The present invention generally relates to a hood covering the space between cylinder banks of an internal-combustion engine which are arranged in a V-shape.
German Patent Specification (DE-PS) 36 35 478 shows the construction of a housing which, in a gastight manner, encloses a ram pipe of an internal-combustion engine and the exhaust pipes which lead fuel gases from cylinder heads to the ram pipe. The cooled housing is situated in the space between the cylinder banks of the internal-combustion engine which are arranged in a V-shape. The housing comprises a bottom part and a top part, of which the latter has contact surfaces at the cylinder heads as well as at the crankcase.
For the gastight enclosure of the ram pipe and of the exhaust pipes leading to the ram pipe, the contact surfaces at the cylinder heads must be sealed off by the cylinder heads and the top part of the housing (which is not shown), and, in addition, the top part of the housing must be provided with a cover. Further, a tight contact must be provided between the top part of the housing and the bottom part of the housing or, if the exhaust-gas-tight space is delimited by the walls of the crankcase and not by a bottom part of the housing, between the top part of the housing and the crankcase.
Because of the occurring high temperatures, high-temperature resistant graphite seals are required in the sealing areas which, however, have the disadvantage of low ductility. Since the top part of the housing rests on a crankcase and at the same time, forms sealing surfaces with the cylinder heads, and it should be possible to sue high-temperature-resistant seals of only low ductility, if manufacturing tolerances are set that are as narrow as possible in order to achieve positional tolerances that are as low as possible which, however, results in high manufacturing costs.
Because of the unavoidable tolerances and the considerable thermal warping occurring during the operation of the internal-combustion engine, high prestresses must be effective in the area of the sealing surfaces in order to avoid the developing of leaks. However, high prestresses require high screwing forces which are introduced into the crankcase and the cylinder heads and may result in undesirable deformations of the cylinder liners or other parts of the internal-combustion engine.
The present invention is based on an object of ensuring the sealing-off of a space between two cylinder banks of a V-engine which is covered by a hood without special requirements with respect to manufacturing tolerances or without requiring a particularly high ductility of the seals, and without requiring that high forces be introduced into disadvantageous areas of the engine for achieving a good sealing effect.
In a construction of the above-mentioned type, this object and other objects are achieved by constructing the hood with a central hood part which rests only against the crankcase and not against the cylinder heads, and with wedge-shaped hood parts which are inserted into V-shaped openings between the central housing part and the cylinder heads. Thus, the different sealing areas are assigned to separate components which are fastened separately from one another and can be slid with respect to one another. By the separate fastening in connection with the special construction of the hood parts, the contact pressures and thus the sealing effect are independent of the positional tolerances arising as a result of manufacturing tolerances. Therefore, lower prestresses may be provided from the start in the area of the sealing surfaces, whereby the stress of the engine components as a result of forces to be introduced is also lowered.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.